1. Field of the Invention
The invention concerns an isolation element for the isolation of vibrations and/or heat, which are propagated in a medium such as soil, as well as the application of such isolation elements in connection with vibration isolation measures.
2. Description of the State of the Art
Vibrations, which are generated in a medium such as soil or water, and which are propagated through this medium, can cause damage to structures, which are located on or in this medium. Vibrations can be generated by a variety of sources, for example by vehicles, machines, blasting or earthquakes. Many attempts have been made to eliminate the propagation of vibrations, in order to protect structures, machines or installations. As a result of such measures, as a secondary effect, it is also possible to isolate the propagation of heat.
Open trenches in the soil are effective measures to protect buildings and other structures in the ground against oscillations and vibrations. Another common method of vibration isolation is to arrange concrete or steel barriers in the ground. Their vibration efficiency, however, is significantly lower than that of open trenches. Swedish Patent Document No. SE, B, 430,620 shows a method for vibration isolation with the aid of one or several membranes, which are installed in the ground, and an arrangement for the implementation of this method. This method is characterized by a membrane or connected membranes. which contain a medium such as air, water or similar agents, and which are made of plastic or similar material, and which are installed in the ground vertically or inclined for instance by means of pressing, vibrating, driving, jetting or a combination of these methods, with the aim of absorbing the vibration energy and to reduce the oscillation energy. The membrane is provided at the upper end with a valve body, through which the pressure in the membrane can be varied before, during or after installation. The membrane can at the lower end be provided with a beam-like arrangement, which during the installation phase creates an opening in the soil of required width. The membrane or membranes can, for example, be installed using a fork-like tool. The described method is expensive and there exists a risk that one or several receptacles are damaged by a sharp article located in the ground.
Swedish Patent Document No. SE, B. 460.062 shows an arrangement for vibration isolation and/or heat isolation. The arrangement comprises membranes which can be installed in a medium such as soil or water. The membranes consist of a flexible, external, relatively stiff covering membrane, which is impermeable with respect to the mentioned medium, and at least one additional flexible inner membrane element consisting of a diffusion-tight material. The inner membrane surrounds a closed space consisting of p double-folded foil, which is welded together to form a receptacle and cells or channels filled with air, gas, liquid or foam or a combination thereof on the side surfaces of the receptacle. The cells or channels of one side of the foil are separated from the cells and channels of the other side of the foil, whereby one (or several) chambers are created between them which can either be filled with air, gas, liquid or foam. A valve can be arranged at the inner membrane in order to make it possible to fill the space with an appropriate material and with desired pressure. The risk of puncturing of the multi-layered membrane is thereby reduced. Damage to one or several chambers do not affect the vibration isolation effectiveness of the membrane. The covering envelope is so stiff that it can distribute variations of the earth pressure. However, the above mentioned disadvantage of high installation cost remains.
In built-up areas, it is common to first excavate a trench in the ground, which is filled with a suitable stabilizing liquid in order to assure the stability of the trench during installation. For the installation of the above mentioned vibration isolation arrangement in a liquid-filled trench, the isolation elements must be provided with special anchors at the bottom of the excavated trench, as the buoyancy of the gas-filled cushions can be considerable. The anchoring can be provided by heavy concrete blocks which are attached in advance to the lower end of the cushions. Alternatively, the cushions can be connected to ground anchors which are installed at the bottom of the trench. The installation of concrete blocks requires the lifting of heavy loads. In addition, the trench must be excavated to greater depth in order to provide space for the anchoring weights. The isolation elements must be installed accurately in the trench in order to achieve a continuous isolation barrier. In practice, it can be difficult to place the flexible cushions with sufficient precision, in order to assure vertical and laterial continuity of the isolation barrier.